Growing degree days (GDD) are commonly used to schedule the beginning of spring nitrogen fertilizer applications in grass seed crops. Typically, 200 GDD (base 0 C) from January 1st is used as the opening date of spring nitrogen fertilizer applications. This number of GDD marks the beginning of the period that the average daily temperature reaches 5 C (41 F) and as a result, grass seed crops resume growth after winter quiescence.
The current (February 13th) GDD is 197 GDD at Hyslop Farm near Corvallis. At the current rate of GDD accumulation, 200 GDD should be attained on the 14th. The long-term average date for attaining 200 GDD is February 14th.